Referring to FIG. 1, a conventional air intake valve apparatus applying for pneumatic gun is illustrated, the air intake valve assembled within a magazine, comprises a valve base 30, a stem 32 configured through the valve base 30 inside for being driving and a spring 34 used to bias the stem 32. Please also referring to FIG. 2, an air-introducing eyelet 302 and an air-exhausting eyelet 304 are configured on the valve base 30. Regularly, since the stem 32 is biased by the spring so as to be maintained on a position which blocking the air-introducing eyelet 302, when the stem 32 hit by a force forwarding the arrow direction, the stem 32 would be shifted forward to the direction forcing the spring then pushed back to the original position by the spring. At the same time the stem is pushed by the force, air could flow into the valve base 30 through the air-introducing eyelet 302 and be released from the valve base 30 through the air-exhausting eyelet 304.
The stem 32 further has a first portion 322 correspondingly contacting with the spring, a second portion 324 extending to the external side of the valve base 30 partly and a cylinder stick 326 mounted between the first portion 322 and the second portion 324. In this embodiment, the first portion 322 is formed in a trump shape and its external side surface is a flat surface to be biased by the spring and maintain the air-introducing eyelet 302 on a blocking position. Excepting to the biasing force generated by the spring, the stem 32 itself also takes the force made by air on the outside of the first portion 322. When the pressure is higher, the force made by air on the outside of the first portion 322 is correspondingly raising. In other word, along with different air pressures forced on the stem 32, the force hit the stem 32 is correspondingly changed.
Thereby, when the pneumatic gun uses different air pressure for conducting, the force applying on the stem of the air intake valve is also different. Therefore, the air intake valve must be adapted or replaced proper items before executing normal functions.